The present invention relates to a method for lifting large storage tanks off the ground by using pressurized bags.
Large storage tanks holding environmentally hazardous products require inspection and maintenance to prevent the products from leaking and contaminating the surrounding soil and ground water supplies. Contamination and pollution of soil and water in the area of the tank can cause the owner enormous cleanup expense. Also, the tank can settle into the ground causing water to form pools around the tank increasing the possibility of corrosion.
Inspection and maintenance of the tank requires temporarily draining the tank. It is important that maintenance be done quickly to minimize the loss of valuable storage space. Inspection of the tank floor from inside the tank is highly inaccurate and cannot detect a faulty foundation or corrosion under the tank.
The preferred prior art method to prevent or correct leakage from the tank is to lift the tank so as to inspect and repair the tank floor from underneath the tank. After the tank is lifted, the bottom of the tank floor can be inspected, sand blasted, repainted, and cathodic protection installed. While the tank is lifted, foundation problems can be rectified and the general condition of the foundation can be upgraded. The foundation can be raised to compensate for any settling that has occurred over time. Improvements such as an impervious layer, leakage detectors, and drainage systems can be installed on the tank foundation while the tank is lifted.
Prior methods for tank lifting have required "hot" work, such as welding and torch cutting on the tank to provide attachment points to the tank for the use of hydraulic lifts. This hot work requires degassing the tank to prevent explosions. In a crowded tank farm, the danger of explosion is always present or difficult to control. Moreover, if the tank to be lifted is very large, holes must be cut in the floor of the tank so that the hydraulic lifts can be placed under the center of the tank floor. Thus, there is a need for providing a procedure of lifting storage tanks without encountering the considerable disadvantages of the prior art methods.